Linear and nonlinear optical response dependency on the crystallite size of CdTe and its structural properties

Abstract

Cadmium telluride QD thin films of thickness (10→57 nm) has been successfully synthesized using inert gas condensation. The structure of thin films was examined by grazing incident in-plane X-ray diffraction (GIIXD), revealing a hexagonal polymorph structure. A strong confinement regime was achieved where the attained radius (from ~2.6 to 6 nm) of particle size of thin films was smaller than the Bohr radius of their bulk CdTe (~7.3 nm). Linear and nonlinear optical properties were affected by changing the particle size. The optical gap is higher than that of bulk CdTe, it increased from 2.44 to 2.8 eV as film thickness decreased from 57 to 10 nm. All optical parameters such as dispersion parameters (Eso and Ed), oscillator strength (f), lattice dielectric constant (εL), static dielectric constant (εo) and refractive index (no) were increased with film thickness. Likewise, the linear and nonlinear susceptibility (X(1), X(3)) besides nonlinear refractive index (n2) increased with film thickness.